query execution time faster with geqo on than off: bug?

I've encountered a query with 11 joins whose execution time (i.e., the time
not taken up by planning) is significantly faster with geqo on rather than
off. This is surprising to me and seems like it might be a bug in the
planner, so I am posting it here rather than to -performance.

The query is below, along with EXPLAIN ANALYZE results with geqo on and
off. The server version is 9.4.4. The various geqo options are all set to
the default. join_collapse_limit is set to 12 (the query is much slower
with it set to the default of 8). Let me know what other information might
be helpful in debugging this further. Thanks!

QUERY:

SELECT ex.ex, ex.lv, ex.tt, ex.td, dnsrc.ex AS trex,
((uiuq_score(array_agg(ap.ui), array_agg(ap.uq)) +
uiuq_score(array_agg(apsrc.ui), array_agg(apsrc.uq))) / 2) AS trq
FROM ex
INNER JOIN lv ON (lv.lv = ex.lv)
INNER JOIN dn ON (dn.ex = ex.ex)
INNER JOIN mn ON (mn.mn = dn.mn)
INNER JOIN ap ON (ap.ap = mn.ap)
INNER JOIN dn AS dn2 ON (dn2.mn = dn.mn)
INNER JOIN dn AS dn3 ON (dn3.ex = dn2.ex)
INNER JOIN dn AS dnsrc ON (dnsrc.mn = dn3.mn)
INNER JOIN mn AS mnsrc ON (mnsrc.mn = dnsrc.mn)
INNER JOIN ap AS apsrc ON (apsrc.ap = mnsrc.ap)
INNER JOIN ex AS exsrc ON (exsrc.ex = dnsrc.ex)
INNER JOIN lv AS lvsrc ON (lvsrc.lv = exsrc.lv)
WHERE
dn.ex != dn2.ex AND
dn3.ex != dnsrc.ex AND
mn.ap != mnsrc.ap AND
dn.ex != dnsrc.ex AND
lcvc(lv.lc, lv.vc) IN ('zul-000') AND
lcvc(lvsrc.lc, lvsrc.vc) IN ('gle-000') AND
exsrc.tt IN ('doras')
GROUP BY ex.ex, dnsrc.ex
ORDER BY trq desc LIMIT 2000;

EXPLAIN ANALYZE with geqo on:

QUERY PLAN

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Limit (cost=3603.82..3603.82 rows=2 width=57) (actual
time=623.322..623.326 rows=31 loops=1)
-> Sort (cost=3603.82..3603.82 rows=2 width=57) (actual
time=623.321..623.321 rows=31 loops=1)
Sort Key: (((uiuq_score(array_agg(ap.ui), array_agg(ap.uq)) +
uiuq_score(array_agg(apsrc.ui), array_agg(apsrc.uq))) / 2))
Sort Method: quicksort Memory: 27kB
-> HashAggregate (cost=3603.60..3603.82 rows=2 width=57) (actual
time=622.074..623.283 rows=31 loops=1)
Group Key: ex.ex, dnsrc.ex
-> Nested Loop (cost=3075.23..3603.59 rows=2 width=57)
(actual time=8.023..620.761 rows=766 loops=1)
-> Nested Loop (cost=3075.17..3603.43 rows=2
width=55) (actual time=8.009..619.417 rows=766 loops=1)
Join Filter: (mn.ap <> mnsrc.ap)
Rows Removed by Join Filter: 3793
-> Hash Join (cost=3075.08..3603.21 rows=2
width=63) (actual time=7.984..610.206 rows=4559 loops=1)
Hash Cond: (dn.ex = ex.ex)
-> Nested Loop (cost=3.04..510.58
rows=20564 width=26) (actual time=0.918..509.574 rows=1047967 loops=1)
Join Filter: (dn.ex <> dnsrc.ex)
Rows Removed by Join Filter: 5396
-> Nested Loop (cost=2.92..277.03
rows=118 width=22) (actual time=0.913..113.830 rows=40525 loops=1)
-> Nested Loop
(cost=2.87..267.76 rows=118 width=16) (actual time=0.899..60.170
rows=40525 loops=1)
-> Hash Join
(cost=2.76..266.08 rows=1 width=12) (actual time=0.878..5.057 rows=1254
loops=1)
Hash Cond: (
exsrc.lv = lvsrc.lv)
-> Nested Loop
(cost=0.43..263.08 rows=871 width=16) (actual time=0.169..4.626 rows=1516
loops=1)
-> Nested
Loop (cost=0.34..164.79 rows=871 width=20) (actual time=0.138..1.180
rows=1516 loops=1)
->
Nested Loop (cost=0.23..155.09 rows=5 width=12) (actual time=0.097..0.306
rows=43 loops=1)

-> Index Scan using ex_tt_idx on ex exsrc (cost=0.11..2.57 rows=2
width=8) (actual time=0.056..0.061 rows=5 loops=1)

Index Cond: (tt = 'doras'::text)

-> Index Scan using dn_ex_idx on dn dnsrc (cost=0.11..75.55 rows=71
width=8) (actual time=0.027..0.046 rows=9 loops=5)

Index Cond: (ex = exsrc.ex)
->
Index Only Scan using dn_mn_ex_key on dn dn3 (cost=0.11..1.13 rows=81
width=8) (actual time=0.008..0.015 rows=35 loops=43)

Index Cond: (mn = dnsrc.mn)

Filter: (ex <> dnsrc.ex)

Rows Removed by Filter: 1

Heap Fetches: 0
-> Index
Scan using mn_pkey on mn mnsrc (cost=0.09..0.10 rows=1 width=8) (actual
time=0.002..0.002 rows=1 loops=1516)
Index
Cond: (mn = dnsrc.mn)
-> Hash
(cost=2.32..2.32 rows=1 width=4) (actual time=0.026..0.026 rows=1 loops=1)
Buckets:
1024 Batches: 1 Memory Usage: 1kB
-> Index
Scan using lv_lcvc_idx on lv lvsrc (cost=0.11..2.32 rows=1 width=4)
(actual time=0.024..0.025 rows=1 loops=1)
Index
Cond: (lcvc(lc, vc) = 'gle-000'::bpchar)
-> Index Scan using
dn_ex_idx on dn dn2 (cost=0.11..0.98 rows=71 width=8) (actual
time=0.005..0.040 rows=32 loops=1254)
Index Cond: (ex =
dn3.ex)
-> Index Scan using ap_pkey
on ap apsrc (cost=0.06..0.07 rows=1 width=10) (actual time=0.001..0.001
rows=1 loops=40525)
Index Cond: (ap =
mnsrc.ap)
-> Index Only Scan using
dn_mn_ex_key on dn (cost=0.11..1.13 rows=81 width=8) (actual
time=0.003..0.006 rows=26 loops=40525)
Index Cond: (mn = dn2.mn)
Filter: (ex <> dn2.ex)
Rows Removed by Filter: 1
Heap Fetches: 728
-> Hash (cost=3049.48..3049.48 rows=2149
width=41) (actual time=5.575..5.575 rows=2105 loops=1)
Buckets: 1024 Batches: 1 Memory
Usage: 121kB
-> Nested Loop (cost=0.19..3049.48
rows=2149 width=41) (actual time=0.044..5.191 rows=2105 loops=1)
-> Index Scan using
lv_lcvc_idx on lv (cost=0.11..2.32 rows=1 width=4) (actual
time=0.013..0.013 rows=1 loops=1)
Index Cond: (lcvc(lc,
vc) = 'zul-000'::bpchar)
-> Index Scan using ex_lv_idx
on ex (cost=0.09..3017.95 rows=2921 width=41) (actual time=0.031..4.834
rows=2105 loops=1)
Index Cond: (lv = lv.lv)
-> Index Scan using mn_pkey on mn
(cost=0.09..0.10 rows=1 width=8) (actual time=0.002..0.002 rows=1
loops=4559)
Index Cond: (mn = dn.mn)
-> Index Scan using ap_pkey on ap (cost=0.06..0.07
rows=1 width=10) (actual time=0.001..0.001 rows=1 loops=766)
Index Cond: (ap = mn.ap)
Planning time: 103.653 ms
Execution time: 623.546 ms

EXPLAIN ANALYZE with geqo off:

QUERY PLAN

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Limit (cost=114.58..114.58 rows=1 width=57) (actual
time=11128.861..11128.865 rows=31 loops=1)
-> Sort (cost=114.58..114.58 rows=1 width=57) (actual
time=11128.861..11128.865 rows=31 loops=1)
Sort Key: (((uiuq_score(array_agg(ap.ui), array_agg(ap.uq)) +
uiuq_score(array_agg(apsrc.ui), array_agg(apsrc.uq))) / 2))
Sort Method: quicksort Memory: 27kB
-> HashAggregate (cost=114.47..114.58 rows=1 width=57) (actual
time=11127.638..11128.840 rows=31 loops=1)
Group Key: ex.ex, dnsrc.ex
-> Nested Loop (cost=1.10..114.46 rows=1 width=57) (actual
time=6.716..11126.183 rows=766 loops=1)
-> Nested Loop (cost=1.05..114.38 rows=1 width=55)
(actual time=6.712..11124.683 rows=766 loops=1)
Join Filter: (mn.ap <> mnsrc.ap)
Rows Removed by Join Filter: 3793
-> Nested Loop (cost=0.96..114.27 rows=1
width=63) (actual time=6.709..11111.769 rows=4559 loops=1)
-> Nested Loop (cost=0.90..114.19 rows=1
width=57) (actual time=6.703..11098.471 rows=4559 loops=1)
-> Nested Loop (cost=0.85..110.70
rows=27 width=57) (actual time=0.135..3765.710 rows=1047967 loops=1)
-> Nested Loop
(cost=0.76..107.61 rows=27 width=20) (actual time=0.116..797.027
rows=1047967 loops=1)
Join Filter: ((dn.ex <>
dn2.ex) AND (dn.ex <> dnsrc.ex))
Rows Removed by Join
Filter: 45921
-> Nested Loop
(cost=0.65..85.78 rows=11 width=28) (actual time=0.110..226.986 rows=40525
loops=1)
-> Nested Loop
(cost=0.56..84.54 rows=11 width=20) (actual time=0.103..53.716 rows=40525
loops=1)
-> Nested
Loop (cost=0.45..82.85 rows=1 width=16) (actual time=0.094..1.009
rows=1254 loops=1)
->
Nested Loop (cost=0.33..80.91 rows=1 width=8) (actual time=0.082..0.123
rows=26 loops=1)

-> Nested Loop (cost=0.22..4.65 rows=1 width=4) (actual
time=0.072..0.075 rows=1 loops=1)

-> Index Scan using lv_lcvc_idx on lv lvsrc (cost=0.11..2.32 rows=1
width=4) (actual time=0.022..0.023 rows=1 loops=1)

Index Cond: (lcvc(lc, vc) = 'gle-000'::bpchar)

-> Index Scan using ex_lv_tt_key on ex exsrc (cost=0.11..2.32 rows=1
width=8) (actual time=0.048..0.049 rows=1 loops=1)

Index Cond: ((lv = lvsrc.lv) AND (tt = 'doras'::text))

-> Index Scan using dn_ex_idx on dn dnsrc (cost=0.11..75.55 rows=71
width=8) (actual time=0.009..0.040 rows=26 loops=1)

Index Cond: (ex = exsrc.ex)
->
Index Only Scan using dn_mn_ex_key on dn dn3 (cost=0.11..1.13 rows=81
width=8) (actual time=0.004..0.023 rows=48 loops=26)

Index Cond: (mn = dnsrc.mn)

Filter: (ex <> dnsrc.ex)

Rows Removed by Filter: 1

Heap Fetches: 0
-> Index
Scan using dn_ex_idx on dn dn2 (cost=0.11..0.98 rows=71 width=8) (actual
time=0.005..0.036 rows=32 loops=1254)
Index
Cond: (ex = dn3.ex)
-> Index Scan
using mn_pkey on mn (cost=0.09..0.10 rows=1 width=8) (actual
time=0.003..0.004 rows=1 loops=40525)
Index Cond:
(mn = dn2.mn)
-> Index Only Scan
using dn_mn_ex_key on dn (cost=0.11..1.09 rows=81 width=8) (actual
time=0.003..0.008 rows=27 loops=40525)
Index Cond: (mn =
mn.mn)
Heap Fetches: 728
-> Index Scan using ex_pkey
on ex (cost=0.09..0.10 rows=1 width=41) (actual time=0.002..0.002 rows=1
loops=1047967)
Index Cond: (ex = dn.ex)
-> Index Scan using lv_pkey on lv
(cost=0.06..0.12 rows=1 width=4) (actual time=0.007..0.007 rows=0
loops=1047967)
Index Cond: (lv = ex.lv)
Filter: (lcvc(lc, vc) =
'zul-000'::bpchar)
Rows Removed by Filter: 1
-> Index Scan using ap_pkey on ap
(cost=0.06..0.07 rows=1 width=10) (actual time=0.002..0.002 rows=1
loops=4559)
Index Cond: (ap = mn.ap)
-> Index Scan using mn_pkey on mn mnsrc
(cost=0.09..0.10 rows=1 width=8) (actual time=0.002..0.002 rows=1
loops=4559)
Index Cond: (mn = dnsrc.mn)
-> Index Scan using ap_pkey on ap apsrc
(cost=0.06..0.07 rows=1 width=10) (actual time=0.001..0.001 rows=1
loops=766)
Index Cond: (ap = mnsrc.ap)
Planning time: 163.302 ms
Execution time: 11129.050 ms